Simulated rain addition modifies diurnal patterns and temperature sensitivities of autotrophic and heterotrophic soil respiration in an arid desert ecosystem

摘要

The timing and magnitude of rainfall events in arid and semiarid regions are expected to change dramatically in future decades, which will likely greatly affect regional carbon cycles. To understand how increases in rainfall affect the diurnal patterns and temperature sensitivities (Q(10)) of soil respiration (R-S) and its key components (i.e. heterotrophic respiration (R-H) and autotrophic respiration (R-A)), we conducted a manipulative field experiment in a desert ecosystem of Northwest China. We simulated five different scenarios of future rain regimes (0%, 25%, 50%, 75% and 100% increase over local annual mean precipitation) each month from May to September in 2009. We measured R-S and R-H every three hours on 6 and 16 days after the rain addition, and estimated R-A by calculating the difference between R-S and R-H. We found that rain addition significantly increased the daily mean R-S and its components on the two measurement days during the growing season. However, the diurnal pattern was different between the two respiration components. Rain addition significantly increased the daily Q(10) value of R-H but suppressed that of R-A on Day 6. Rain addition had no influence on daily Q(10) value of both respiration components on Day 16 when soil moisture was lower. In addition, we observed significantly higher daily Q(10) of R-H than R-A under all five rain addition treatments, indicating that microbial respiration is more temperature sensitive than root respiration in a short-time scale in this desert ecosystem. Thus, partitioning soil respiration into its two components, and analyzing the differential responses of R-H and R-A to future climate changes should be considered for more accurate predictions of soil respiration and regional carbon cycle in these arid and semiarid regions. (c) 2015 Elsevier Ltd. All rights reserved.